JP6082848B2 - Thermally expansible microspheres, production method and use thereof - Google Patents

Description

  The present invention relates to a thermally expandable microsphere, a method for producing the same, and an application thereof.

Thermally expandable microspheres having a structure in which a thermoplastic resin is used as an outer shell and a foaming agent is enclosed in the outer shell are generally referred to as thermally expandable microcapsules. As raw material monomers for thermoplastic resins, vinylidene chloride, (meth) acrylonitrile monomers, (meth) acrylic acid ester monomers and the like are usually used. Moreover, hydrocarbons, such as isobutane and isopentane, are mainly used as a foaming agent (refer patent document 1).
When producing the heat-expandable microspheres, a change in vapor pressure may occur in the hydrocarbon as a foaming agent due to heat generated during the polymerization, and the heat-expandable microspheres during the polymerization may expand and / or contract. As a result, the outer shell of the thermally expandable microsphere is not spherical, but has a dent and an irregular shape.

When the shape of the thermally expandable microsphere has a dent, the filling efficiency is deteriorated as compared with the case of a spherical shape. As a result, when producing a resin composition such as a masterbatch containing thermally expandable microspheres and a resin, the thermally expandable microspheres and the resin cannot be uniformly mixed, and the thermally expandable microspheres are not bonded to the resin. May overflow when mixing. That is, a sufficient amount of thermally expandable microspheres cannot be mixed with the resin, and the workability during the production of the resin composition is greatly reduced.
Further, if the thermally expandable microsphere has a concave shape with a dent, the pressure of the foaming agent is not uniformly applied to the outer shell during expansion, so that sufficient expandability cannot be obtained. In particular, when a resin composition containing thermally expandable microspheres and a resin is applied to resin molding such as extrusion molding, injection molding, calendar molding, press molding, etc., a higher pressure is applied, so that the thermal expansion with a dent is applied. When the microspheres are subjected to strong shear, the stress is applied unevenly. For this reason, there is a case where the thermally expandable microspheres are destroyed, and as a result, there is a problem that the expandability of the thermally expandable microspheres is impaired during the resin molding.
From the above situation, the development of thermally expandable microspheres having a more spherical shape is desired.

US Pat. No. 3,615,972

  An object of the present invention is to provide a thermally expandable microsphere having a substantially spherical shape, excellent expandability, and good workability when mixed with a resin, a method for producing the same, and a use thereof.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a thermoplastic resin obtained by polymerizing a specific polymerizable component as an outer shell and encapsulated a foaming agent that requires a specific hydrocarbon. The present inventors have found that the above-described problems can be achieved with thermally expandable microspheres, and have reached the present invention.
That is, the thermally expandable microsphere according to the present invention is a thermally expandable microsphere composed of an outer shell made of a thermoplastic resin and a foaming agent encapsulated therein and vaporized by heating. The plastic resin essentially comprises a methacrylic acid ester monomer and a carboxyl group-containing monomer, and the nitrile monomer has a total amount of 100 parts by weight of the methacrylic acid ester monomer and the carboxyl group-containing monomer. On the other hand, it is obtained by polymerizing 0 to 30 parts by weight of a polymerizable component, and the foaming agent is a thermally expandable microsphere essentially comprising a hydrocarbon having 8 or more carbon atoms.

This thermally expandable microsphere may further satisfy at least one requirement selected from the following (1) to (5).
(1) The degree of compression is less than 25%.
(2) The gelation rate after being immersed in DMF for 72 hours is 90% or less.
(3) The weight ratio of the methacrylic acid ester monomer is 40 to 85% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer.
(4) The maximum expansion temperature is 100 ° C. or higher.
(5) The yellowing degree ΔYI when heated at 180 ° C. for 10 minutes is 30 or less.

The method for producing thermally expandable microspheres according to the present invention comprises a step of dispersing an oily mixture containing a polymerizable component, a foaming agent, and a polymerization initiator in an aqueous dispersion medium, and polymerizing the polymerizable component. The polymerizable component is essentially a methacrylic acid ester monomer and a carboxyl group-containing monomer, and the nitrile monomer is a total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer. It is a manufacturing method which is a polymerizable component which is 0 to 30 parts by weight with respect to 100 parts by weight, and the blowing agent is essentially a hydrocarbon having 8 or more carbon atoms.
The method for producing the thermally expandable microsphere may further satisfy at least one requirement selected from the following (A) to (C).

(A) The said polymerization initiator is 0.9-10 weight part with respect to 100 weight part of total amounts of the said methacrylic ester monomer and a carboxyl group-containing monomer.
(B) The weight ratio of the methacrylic acid ester monomer is 40 to 85% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer.
(C) In the polymerizable component, the crosslinking agent is 0 to 0.4 parts by weight with respect to 100 parts by weight of the total amount of the methacrylic acid ester monomer, the carboxyl group-containing monomer and the nitrile monomer. is there.
The hollow particles of the present invention are particles obtained by heating and expanding the thermally expandable microspheres and / or the thermally expandable microspheres obtained by the method for producing the thermally expandable microspheres.

The composition of the present invention comprises at least one granular material selected from the above-mentioned thermally expandable microspheres, the thermally expandable microspheres obtained by the method for producing the thermally expandable microspheres, and the above hollow particles, and a substrate A composition comprising the components.
The molded product of the present invention is formed by molding the above composition. Here, the yellowing degree ΔYI is preferably 30 or less.

The thermally expandable microspheres of the present invention are almost spherical, have excellent expandability, and have good workability when mixed with a resin.
The method for producing thermally expandable microspheres of the present invention can efficiently produce thermally expandable microspheres that are substantially spherical, have excellent expandability, and have good workability when mixed with a resin.

The hollow particles of the present invention, like the thermally expandable microspheres of the present invention, are substantially spherical and have good workability when mixed with a resin.
The composition of the present invention has excellent expandability and good workability during production.
Since the molded product of the present invention is manufactured from the thermally expandable microspheres of the present invention, it is sufficiently lightweight.

It is the schematic which shows an example of a thermally expansible microsphere. It is the schematic which shows an example of a hollow particle.

[Method for producing thermally expandable microspheres]
The method for producing thermally expandable microspheres of the present invention comprises a step of dispersing an oily mixture containing a polymerizable component, a foaming agent, and a polymerization initiator in an aqueous dispersion medium and polymerizing the polymerizable component (hereinafter referred to as “polymerizable component”). Then, it may be referred to as a polymerization step).
The polymerizable component is a component that becomes a thermoplastic resin that forms the outer shell of the thermally expandable microsphere by polymerization. The polymerizable component is a component which essentially includes a monomer component and may contain a crosslinking agent. The monomer component means a radical polymerizable monomer having one polymerizable double bond and is a component capable of addition polymerization. The crosslinking agent means a radically polymerizable monomer having a plurality of polymerizable double bonds, and is a component that introduces a bridge structure into the thermoplastic resin.

The polymerizable component essentially comprises a methacrylic acid ester monomer and a carboxyl group-containing monomer (classified as a monomer component).
The methacrylic acid ester monomer is not particularly limited, but is methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate. , N-stearyl methacrylate, butoxydiethylene glycol methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, benzyl methacrylate, β-carboxyethyl methacrylate, ethoxy-diethylene glycol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxy Propyl methacrylate, 2-methacryloilo Shiechiru-2-hydroxyethyl phthalic acid, glycidyl methacrylate and the like. Among these, methyl methacrylate is preferable because the expandability of the thermally expandable microspheres obtained is excellent.

The carboxyl group-containing monomer is not particularly limited as long as it has one or more free carboxyl groups per molecule, but unsaturated monomers such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid. Carboxylic acid; unsaturated dicarboxylic acid such as maleic acid, itaconic acid, fumaric acid, citraconic acid, chloromaleic acid; anhydride of unsaturated dicarboxylic acid; monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, fumarate Examples thereof include unsaturated dicarboxylic acid monoesters such as monoethyl acid, monomethyl itaconate, monoethyl itaconate and monobutyl itaconate. These carboxyl group-containing monomers may be used alone or in combination of two or more. In the carboxyl group-containing monomer, some or all of the carboxyl groups may be neutralized during polymerization or after polymerization. Of the above carboxyl group-containing monomers, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and itaconic acid are preferred, acrylic acid and methacrylic acid are more preferred, and the resulting heat-expandable microspheres have high heat resistance. Methacrylic acid is particularly preferred.
The weight ratio of the methacrylic acid ester monomer is not particularly limited, but is preferably 40 to 85% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer. Preferably it is 45-80 weight%, More preferably, it is 50-75 weight%, Most preferably, it is 55-70 weight%. When the weight ratio of the methacrylic acid ester monomer is less than 40% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer, the shape of the resulting heat-expandable microsphere has a dent. As a result, workability and expansion ratio when mixed with a resin may decrease. On the other hand, if the weight ratio of the methacrylic acid ester monomer exceeds 85% by weight, the heat resistance of the resulting heat-expandable microspheres may be lowered.

  The total weight ratio of the methacrylic acid ester monomer and the carboxyl group-containing monomer is not particularly limited, but is preferably more than 70% by weight of the entire polymerizable component, more preferably more than 80% by weight, More preferably, it is more than 90% by weight. About this weight ratio, a preferable upper limit is 100 weight% of the whole polymerizable component. When the weight ratio is 70% by weight or less of the entire polymerizable component, the heat-expandable microspheres obtained have dents, and workability and expandability when mixed with a resin are lowered.

The polymerizable component may contain, as a monomer component, other monomer components that can be polymerized with a methacrylic acid ester monomer and a carboxyl group-containing monomer. Examples of other monomer components include nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile; vinyl halide monomers such as vinyl chloride; vinylidene chloride Vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, etc .; methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, stearyl Acrylic acid ester monomers such as acrylate, phenyl acrylate, isobornyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-hydroxyethyl acrylate; acrylamide, substituted acrylamide (Meth) acrylamide monomers such as methacrylamide, substituted methacrylamide; maleimide monomers such as N-phenylmaleimide and N-cyclohexylmaleimide; styrene monomers such as styrene and α-methylstyrene; ethylene Ethylene unsaturated monoolefin monomers such as vinyl propylene and isobutylene; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketone monomers such as vinyl methyl ketone; N-vinylcarbazole N-vinyl monomers such as N-vinylpyrrolidone; vinyl naphthalene salts and the like.
In the polymerizable component, the weight ratio of the nitrile monomer is 0 to 30 parts by weight, preferably 0 to 20 parts per 100 parts by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer. Parts by weight, more preferably 0 to 10 parts by weight, still more preferably 0 to 5 parts by weight, particularly preferably 0 parts by weight. When the weight ratio of the nitrile monomer exceeds 30 parts by weight with respect to 100 parts by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer, the resulting heat-expandable microspheres are indented. And workability and expandability when mixed with a resin are reduced.

The glass transition temperature (Tg) of the homopolymer of the monomer component may be an index for selecting the monomer component. Among the monomer components, if the Tg of the homopolymer is preferably more than 40 ° C., more preferably more than 50 ° C., still more preferably more than 60 ° C., and particularly preferably more than 70 ° C., it is almost spherical and expands. Thermally expandable microspheres with excellent properties can be obtained.
The monomer component having a Tg of the homopolymer exceeding 40 ° C. is not particularly limited. For example, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, vinyl chloride, t-butyl acrylate , Stearyl acrylate, phenyl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, 2- Hydroxyethyl methacrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-phenylmaleimi N-cyclohexylmaleimide, styrene, N-vinyl carbazole, N-vinyl pyrrolidone, vinyl naphthalene salt, acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, cinnamic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid Chloromaleic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate and the like. Among these, t-butyl acrylate, stearyl acrylate, phenyl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl Methacrylate, benzyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-phenylmaleimide, N-cyclohexylmaleimide, styrene, N-vinylcarbazole, N-vinylpyrrolidone, vinylnaphthalene salt, acrylic acid, methacrylic acid , Etacrylic acid, Crotonic acid, Cinnamic acid, Maleic acid, Itako Acid, fumaric acid, citraconic acid, chloro maleic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate and the like. Thermally expandable microspheres obtained by polymerizing polymerizable components containing these monomer components are preferable because the degree of yellowing becomes small.

According to “POLYMER HANDBOOK, third edition, J. Bradrup and E. H Immergut, Ed., JOHNWILEY & SONS, Inc. 1989.”, for example, polymethyl methacrylate 105 ° C, polyethyl methacrylate 65 ° C, polyacrylic acid 106 ° C, polymethacrylic acid 228 ° C, polyacrylonitrile 125 ° C, polymethacrylonitrile 120 ° C, and polyacrylamide 165 ° C.
If the monomer component used as the polymerizable component has a glass transition temperature of less than 40 ° C. of the homopolymer, the resulting thermally expandable microspheres may have dents and the expansion performance may be reduced. . On the other hand, if the monomer component used as the polymerizable component has a glass transition temperature of more than 250 ° C., the expansion performance of the resulting thermally expandable microspheres may be lowered.

As described above, the polymerizable component may contain a crosslinking agent. By polymerizing using a cross-linking agent, in the thermally expandable microspheres obtained, a decrease in the retention rate (encapsulation retention rate) of the encapsulated foaming agent during thermal expansion is suppressed, and effective thermal expansion can be achieved. it can.
Although it does not specifically limit as a crosslinking agent, For example, aromatic divinyl compounds, such as divinylbenzene; Allyl methacrylate, triacryl formal, triallyl isocyanate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1 , 4-butanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, PEG # 200 di (meth) acrylate, PEG # 600 di (meth) acrylate, trimethylolpropane trimethacrylate, pentaerythrul Polyfunctionality such as tall tri (meth) acrylate, dipentaerythritol hexaacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, tricyclodecane dimethanol di (meth) acrylate ( Data) acrylate compounds, and the like. These crosslinking agents may be used alone or in combination of two or more.

There may be no cross-linking agent, but the amount thereof is not particularly limited, and is 0 to 0 parts by weight with respect to 100 parts by weight of the total amount of the methacrylic acid ester monomer, carboxyl group-containing monomer and nitrile monomer. The amount is preferably 0.4 parts by weight, more preferably 0.02 to 0.3 parts by weight, and particularly preferably 0.04 to 0.2 parts by weight. If the crosslinking agent is more than 0.4 parts by weight, the resulting heat-expandable microspheres have dents, the compressibility of the heat-expandable microspheres is greater than 20%, and workability is reduced when mixed with resin. There are things to do.
The foaming agent is a component that is vaporized by heating, and is encapsulated in an outer shell made of a thermoplastic resin of thermally expandable microspheres. The whole shows a property of swelling by heating.

The blowing agent is essentially a hydrocarbon having 8 or more carbon atoms. Examples of the hydrocarbon having 8 or more carbon atoms include linear hydrocarbons such as octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and nonadecane; isooctane, isononane, isodecane, isododecane, 3 -Methylundecane, isotridecane, 4-methyldodecane, isotetradecane, isopentadecane, isohexadecane, 2,2,4,4,6,8,8-heptamethylnonane, isoheptadecane, isooctadecane, isononadecane, 2,6,10 , 14-tetramethylpentadecane and other branched hydrocarbons; cyclododecane, cyclotridecane, hexylcyclohexane, heptylcyclohexane, n-octylcyclohexane, cyclopentadecane, nonylcyclohexa , Decyl cyclohexane, pentadecyl cyclohexane, hexadecyl cyclohexane, heptadecyl cyclohexane, alicyclic hydrocarbons such as octadecyl cyclohexane. A hydrocarbon having 8 or more carbon atoms is preferable if the boiling point is 100 ° C. or higher because the maximum expansion temperature of the thermally expandable microspheres is improved.
The blowing agent may be used in combination with other blowing agents other than hydrocarbons having 8 or more carbon atoms. Other blowing agents include, for example, hydrocarbons having 3 to 7 carbon atoms such as propane, (iso) butane, (iso) pentane, (iso) hexane, (iso) heptane; petroleum ether; their halides; hydro Examples thereof include fluorine-containing compounds such as fluoroethers; tetraalkylsilanes; compounds that are thermally decomposed by heating to generate gas.

The blowing agent may be linear, branched or alicyclic, and is preferably aliphatic.
The weight ratio of the hydrocarbon having 8 or more carbon atoms in the foaming agent is preferably 20% by weight or more, more preferably 30% by weight or more, and particularly preferably 40% by weight or more of the entire foaming agent. A preferable upper limit of the weight ratio of the hydrocarbon having 8 or more carbon atoms in the blowing agent is 80% by weight. When the weight ratio of the hydrocarbon having 8 or more carbon atoms is less than 20% by weight, the vapor pressure of the hydrocarbon may be increased during the polymerization, and the resulting thermally expandable microsphere may be dented. On the other hand, when the weight ratio of hydrocarbons having 8 or more carbon atoms exceeds 80% by weight, the vapor pressure of the foaming agent is lowered, and the expansion ratio of the resulting thermally expandable microspheres may be lowered.

In the production method of the present invention, the polymerizable component is polymerized in the presence of the polymerization initiator using an oily mixture containing a polymerization initiator together with the polymerizable component and the foaming agent.
The polymerization initiator is not particularly limited, but examples of the peroxide include a generally used peroxide, such as diisopropyl peroxydicarbonate, di-sec-butylperoxydicarbonate, Peroxydicarbonates such as di-2-ethylhexylperoxydicarbonate and dibenzylperoxydicarbonate; Diacyl peroxides such as lauroyl peroxide and benzoyl peroxide; Ketone peroxides such as methylethylketone peroxide and cyclohexanone peroxide; 2 , 2-bis (t-butylperoxy) butane and other peroxyketals; cumene hydroperoxide, hydroperoxides such as t-butyl hydroperoxide; dicumyl peroxide, di-t- Dialkyl peroxides such as chill peroxide; t-hexyl peroxypivalate, peroxy esters such as t-butyl peroxy isobutyrate and the like.

Examples of the azo compound include 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4- Dimethylvaleronitrile), 2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), and the like.
The weight ratio of the polymerization initiator is preferably 0.9 to 10 parts by weight, more preferably 1.2 to 9 parts by weight, and most preferably 1.5 to 8 parts per 100 parts by weight of the polymerizable component. Parts by weight. When the amount is less than 0.9 part by weight with respect to 100 parts by weight of the polymerizable component of the polymerization initiator, the thermally expandable microsphere has a dent, the expansion ratio decreases, and the compressibility of the thermally expandable microsphere. May increase workability when mixed with resin. When the weight ratio of the polymerization initiator exceeds 10 parts by weight with respect to 100 parts by weight of the polymerizable component, the heat resistance decreases.

  The weight ratio of the polymerization initiator is preferably 0.9 to 10 parts by weight, more preferably 1.10 parts by weight with respect to 100 parts by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer. 2 to 9 parts by weight, most preferably 1.5 to 8 parts by weight. When the weight ratio is less than 0.9 parts by weight, the thermally expandable microspheres have dents, the expansion ratio decreases, the compressibility of the thermally expandable microspheres increases, and when mixed with the resin Workability may be reduced. When the weight ratio exceeds 10 parts by weight, the heat resistance is lowered.

In the production method of the present invention, an aqueous suspension in which an oily mixture is dispersed in an aqueous dispersion medium is prepared, and a polymerizable component is polymerized.
The aqueous dispersion medium is a medium mainly composed of water such as ion-exchanged water in which the oily mixture is dispersed, and may further contain an alcohol such as methanol, ethanol or propanol, or a hydrophilic organic solvent such as acetone. Good. The hydrophilicity in the present invention means that it can be arbitrarily mixed with water. Although there is no limitation in particular about the usage-amount of an aqueous dispersion medium, it is preferable to use 100-1000 weight part aqueous dispersion medium with respect to 100 weight part of polymeric components.

The aqueous dispersion medium may further contain an electrolyte. Examples of the electrolyte include sodium chloride, magnesium chloride, calcium chloride, sodium sulfate, magnesium sulfate, ammonium sulfate, and sodium carbonate. These electrolytes may be used alone or in combination of two or more. Although there is no limitation in particular about content of an electrolyte, it is preferable to contain 0.1-50 weight part with respect to 100 weight part of aqueous dispersion media.
An aqueous dispersion medium is a water-soluble 1,1-substituted compound having a structure in which a hydrophilic functional group selected from a hydroxyl group, a carboxylic acid (salt) group, and a phosphonic acid (salt) group and a hetero atom are bonded to the same carbon atom , Potassium dichromate, alkali metal nitrite, metal (III) halide, boric acid, water-soluble ascorbic acids, water-soluble polyphenols, water-soluble vitamin Bs and water-soluble phosphonic acids (salts) It may contain at least one water-soluble compound. In addition, the water solubility in this invention means the state which melt | dissolves 1g or more per 100g of water.

The amount of the water-soluble compound contained in the aqueous dispersion medium is not particularly limited, but is preferably 0.0001 to 1.0 part by weight, more preferably 0.0003 to 100 parts by weight of the polymerizable component. 0.1 parts by weight, particularly preferably 0.001 to 0.05 parts by weight. If the amount of the water-soluble compound is too small, the effect of the water-soluble compound may not be sufficiently obtained. Moreover, when there is too much quantity of a water-soluble compound, a polymerization rate may fall or the residual amount of the polymeric component which is a raw material may increase.
The aqueous dispersion medium may contain a dispersion stabilizer and a dispersion stabilization auxiliary agent in addition to the electrolyte and the water-soluble compound.

The dispersion stabilizer is not particularly limited, and examples thereof include tricalcium phosphate, magnesium pyrophosphate, calcium pyrophosphate obtained by a metathesis generation method, colloidal silica, alumina sol, magnesium hydroxide and the like. These dispersion stabilizers may be used alone or in combination of two or more.
The blending amount of the dispersion stabilizer is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymerizable component.

The dispersion stabilizing aid is not particularly limited, and examples thereof include a polymer type dispersion stabilizing aid, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, and a nonionic surfactant. Mention may be made of activators. These dispersion stabilizing aids may be used alone or in combination of two or more.
The aqueous dispersion medium is prepared, for example, by blending water (ion-exchanged water) with a water-soluble compound and, if necessary, a dispersion stabilizer and / or a dispersion stabilizing aid. The pH of the aqueous dispersion medium at the time of polymerization is appropriately determined depending on the type of water-soluble compound, dispersion stabilizer, and dispersion stabilization aid.

In the production method of the present invention, polymerization may be carried out in the presence of sodium hydroxide, sodium hydroxide and zinc chloride.
In the production method of the present invention, an oily mixture is suspended and dispersed in an aqueous dispersion medium so that spherical oil droplets having a predetermined particle diameter are prepared.

Examples of the method for suspending and dispersing the oily mixture include, for example, a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.) and the like, and a static dispersion such as a static mixer (for example, manufactured by Noritake Engineering Co., Ltd.) General dispersion methods such as a method using an apparatus, a membrane suspension method, and an ultrasonic dispersion method can be given.
Next, suspension polymerization is started by heating the dispersion in which the oily mixture is dispersed as spherical oil droplets in the aqueous dispersion medium. During the polymerization reaction, it is preferable to stir the dispersion, and the stirring may be performed so gently as to prevent, for example, floating of the monomer and sedimentation of the thermally expandable microspheres after polymerization.

  Although superposition | polymerization temperature is freely set by the kind of polymerization initiator, Preferably it is 30-100 degreeC, More preferably, it controls in the range of 40-90 degreeC. The time for maintaining the reaction temperature is preferably about 0.1 to 20 hours. The initial polymerization pressure is not particularly limited, but is 0 to 5 MPa, more preferably 0.1 to 3 MPa in terms of gauge pressure.

[Thermal expandable microspheres]
As shown in FIG. 1, the thermally expandable microsphere of the present invention is composed of an outer shell (shell) 11 made of a thermoplastic resin and a foaming agent (core) 12 that is contained in the shell and vaporizes when heated. These are thermally expandable microspheres. The thermally expandable microsphere has a core-shell structure, and the thermally expandable microsphere exhibits thermal expandability (property that the entire microsphere expands by heating) as a whole microsphere. The thermoplastic resin, the polymerizable component that is polymerized to become a thermoplastic resin, the monomer component, the crosslinking agent, the foaming agent, and the like constituting the polymerizable component are as described above.
The average particle size of the heat-expandable microspheres is not particularly limited, but is preferably 1 to 100 μm, more preferably 3 to 80 μm, still more preferably 7 to 60 μm, and particularly preferably 10 to 50 μm. When the average particle diameter is smaller than 1 μm, the expansion performance of the thermally expandable microsphere may be lowered. On the other hand, when the average particle size is larger than 100 μm, the filling efficiency is lowered, and workability may be lowered when mixed with the resin.

  The coefficient of variation CV of the particle size distribution of the heat-expandable microspheres is not particularly limited, but is preferably 35% or less, more preferably 30% or less, and particularly preferably 25% or less. The variation coefficient CV is calculated by the following calculation formulas (1) and (2).

(Wherein, s is the standard deviation of the particle size, <x> is an average particle size, x _i is the i-th particle diameter, n is the number of particles.)
The encapsulating rate of the foaming agent is defined as the percentage of the weight of the foaming agent encapsulated in the thermally expandable microspheres relative to the weight of the thermally expandable microspheres. The encapsulating rate of the foaming agent is not particularly limited, but is preferably 1 to 60% by weight, more preferably 3 to 50% by weight, still more preferably 8 to 40% by weight, based on the weight of the thermally expandable microspheres. Particularly preferably, it is 10 to 30% by weight.

The expansion start temperature (Ts) of the thermally expandable microsphere is not particularly limited, but is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, further preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, and most preferably 130. ℃ or more. On the other hand, the upper limit value of the expansion start temperature is preferably 200 ° C. When the expansion start temperature is less than 90 ° C., the heat resistance is low, and the expansion performance of the thermally expandable microsphere may be decreased. On the other hand, when the expansion start temperature exceeds 200 ° C., the maximum foaming temperature is increased, and the expansion performance of the thermally expandable microsphere may be lowered.
The maximum expansion temperature (Tm) of the thermally expandable microsphere is not particularly limited, but is preferably 100 ° C or higher, more preferably 110 ° C or higher, further preferably 120 ° C or higher, particularly preferably 130 ° C or higher, most preferably. Is 140 ° C. or higher. If the maximum expansion temperature of the thermally expandable microsphere is less than 100 ° C., sufficient heat resistance may not be obtained. On the other hand, if the maximum expansion temperature of the thermally expandable microsphere exceeds 300 ° C., a sufficient expansion ratio may not be obtained.

The thermally expandable microspheres obtained by the present invention have a high maximum expansion temperature and are excellent in heat resistance, and are therefore suitable for use in injection molding and the like.
The maximum expansion ratio of the thermally expandable microsphere is not particularly limited, but is preferably 20 times or more, more preferably 30 times or more, still more preferably 40 times or more, particularly preferably 50 times or more, and further preferably 60 times or more. Most preferably, it is 70 times or more. On the other hand, the upper limit of the maximum expansion ratio is preferably 200 times. When the maximum expansion ratio is less than 20 times, a sufficient expansion ratio may not be obtained when the thermally expandable microspheres are contained in the molded article or the like. When the maximum expansion ratio exceeds 200 times, surface roughness may occur in a molded article containing thermally expandable microspheres.

The degree of compression of the heat-expandable microsphere is an index indicating the degree of packing in an aggregate of a large number of heat-expandable microspheres. As shown in the following examples, the compacted bulk density of the heat-expandable microspheres It is calculated by measuring (bulk density in a tightly packed state) and loosened bulk density (bulk density in a loosely packed state) of thermally expandable microspheres. The degree of compressibility of the thermally expandable microspheres also has a negative correlation with the workability when the thermally expandable microspheres and the resin are mixed. That is, when the compressibility of the thermally expandable microspheres is increased, the filling efficiency of the thermally expandable microspheres is decreased, so that workability when the thermally expandable microspheres and the resin are mixed is decreased.
The degree of compression of the heat-expandable microsphere is not particularly limited, but is preferably less than 25%, more preferably less than 20%, even more preferably less than 18%, even more preferably less than 16%, and particularly preferably 14%. Less than, more particularly preferably less than 12%, most preferably less than 10%. If the compressibility of the thermally expandable microspheres is 25% or more, the thermally expandable microspheres have a recessed shape, and the expandability may be reduced because the pressure of the foaming agent is not uniformly applied when heated. is there. In addition, since the heat-expandable microspheres having a concave shape are reduced in filling efficiency, workability may be reduced when the heat-expandable microspheres and the resin are mixed.

The gelation rate of the heat-expandable microsphere is an index indicating the degree of solvent resistance of the thermoplastic resin constituting the outer shell of the heat-expandable microsphere. The sphere is immersed in DMF for 72 hours, the supernatant liquid in which a part of the thermally expandable microsphere is dissolved in the solvent is removed, and the weight of the thermally expandable microsphere remaining as a gel without being dissolved is weighed. Calculated.
The gelation rate of the thermally expandable microspheres is not particularly limited, but is preferably 90% or less, more preferably 85% or less, still more preferably 80% or less, still more preferably 75% or less, and particularly preferably 70. % Or less, more preferably 65% or less, and most preferably 60% or less. When the gelation rate of the heat-expandable microspheres exceeds 90%, the outer shell of the heat-expandable microspheres has a robust thermoplastic resin, so that the expandability is lowered.

The yellowing degree (ΔYI) of the thermally expandable microsphere is an index indicating the degree of heat resistance of the thermoplastic resin constituting the outer shell of the thermally expandable microsphere. As shown in the following examples, the degree of yellowing is measured by heating a measurement object such as a thermally expandable microsphere at 180 ° C. for 10 minutes to measure the yellowness (YI), and the yellowness (YI0) of the standard sample is measured. Calculated by subtracting.
The yellowing degree (ΔYI) of the thermally expandable microsphere is preferably 30 or less, more preferably 25 or less, even more preferably 20 or less, particularly preferably 15 or less, further preferably 10 or less, and most preferably 5 or less. It is. When the degree of yellowing of the heat-expandable microspheres exceeds 30, a molded product containing the heat-expandable microspheres may be colored.

[Hollow particles]
The hollow particles of the present invention are particles obtained by heating and expanding the heat-expandable microspheres described above and the heat-expandable microspheres obtained by the method for producing the heat-expandable microspheres described above. The hollow particles are lightweight and have excellent material properties when included in a composition or a molded product.

Examples of the production method for obtaining the hollow particles include a dry heat expansion method and a wet heat expansion method. The temperature for heat expansion is preferably 80 to 350 ° C.
The average particle diameter of the hollow particles is not particularly limited because it can be designed freely according to the application, but is preferably 0.1 to 1000 μm, more preferably 0.8 to 200 μm. Further, the coefficient of variation CV of the particle size distribution of the hollow particles is not particularly limited, but is preferably 30% or less, and more preferably 25% or less.

Although there is no limitation in particular about the true specific gravity of a hollow particle, Preferably it is 0.010-0.5, More preferably, it is 0.015-0.3, Especially preferably, it is 0.020-0.2.
The yellowing degree (ΔYI) of the hollow particles is not particularly limited, but is preferably 30 or less, more preferably 25 or less, even more preferably 20 or less, particularly preferably 15 or less, still more preferably 10 or less, and most preferably. Is 5 or less. If the yellowing degree of the hollow particles exceeds 30, the molded product containing the hollow particles may be colored. In addition, the yellowing degree (ΔYI) of the hollow particles can be obtained by the method shown in the following examples, similarly to the yellowing degree of the thermally expandable microspheres.

As shown in FIG. 2, the hollow particles (1) may be composed of fine particles (4 and 5) attached to the outer surface of the outer shell (2). There is.
The term “adhesion” as used herein may be simply the state (4) in which the fine particle fillers (4 and 5) are adsorbed on the outer surface of the outer shell (2) of the fine particle-adhered hollow particles (1). This means that the thermoplastic resin constituting the outer shell in the vicinity may be melted by heating, and the fine particle filler may sink into the outer surface of the outer shell of the fine particle-attached hollow particle and be fixed (5). The particle shape of the fine particle filler may be indefinite or spherical. In the fine particle-adhered hollow particles, workability (handling) during use is improved.

The average particle size of the fine particles is appropriately selected depending on the hollow body used, and is not particularly limited, but is preferably 0.001 to 30 μm, more preferably 0.005 to 25 μm, and particularly preferably 0.01 to 20 μm. .
Various particles can be used as the fine particles, and any of inorganic materials and organic materials may be used. Examples of the shape of the fine particles include a spherical shape, a needle shape, and a plate shape.

The fine particles are not particularly limited, but when the fine particles are organic, for example, metal soaps such as magnesium stearate, calcium stearate, zinc stearate, barium stearate, lithium stearate; polyethylene wax, lauric acid amide, myristic acid Synthetic waxes such as amide, palmitic acid amide, stearic acid amide, and hardened castor oil; and organic fillers such as polyacrylamide, polyimide, nylon, polymethyl methacrylate, polyethylene, and polytetrafluoroethylene. When the fine particles are inorganic, for example, talc, mica, bentonite, sericite, carbon black, molybdenum disulfide, tungsten disulfide, fluorinated graphite, calcium fluoride, boron nitride, etc .; others, silica, alumina, mica, colloidal Examples thereof include inorganic fillers such as calcium carbonate, heavy calcium carbonate, calcium hydroxide, calcium phosphate, magnesium hydroxide, magnesium phosphate, barium sulfate, titanium dioxide, zinc oxide, ceramic beads, glass beads, and crystal beads.
The average particle diameter of the fine particles is preferably 1/10 or less of the average particle diameter of the fine particle-attached hollow particles. Here, the average particle size means the average particle size of primary particles.

When the hollow particles are fine particle-adhered hollow particles, if the fine particle-adhered hollow particles are blended in the composition described later as hollow particles, they are useful as a coating composition or an adhesive composition.
The fine particle-attached hollow particles can be obtained, for example, by heating and expanding fine particle-attached thermally expandable microspheres. As a method for producing fine particle-attached hollow particles, a step of mixing thermally expandable microspheres and fine particles (mixing step), and heating the mixture obtained in the mixing step to a temperature above the softening point, the heat A production method including a step (attachment step) of inflating the expandable microspheres and attaching fine particles to the outer surface of the obtained hollow particles is preferable.

  The true specific gravity of the fine particle-attached hollow particles is not particularly limited, but is preferably 0.01 to 0.5, more preferably 0.03 to 0.4, particularly preferably 0.05 to 0.35. Most preferably, it is 0.07-0.30. When the true specific gravity of the fine particle-adhered hollow particles is less than 0.01, the durability may be insufficient. On the other hand, when the true specific gravity of the fine particle-attached hollow particles is larger than 0.5, the effect of reducing the specific gravity is reduced. Sometimes.

[Composition and molded product]
The composition of the present invention comprises at least one kind selected from the thermally expandable microspheres of the present invention, the thermally expandable microspheres obtained by the method for producing the thermally expandable microspheres of the present invention, and the hollow particles of the present invention. A granular material and a base material component are included.
The base material component is not particularly limited. For example, rubbers such as natural rubber, butyl rubber, silicon rubber, ethylene-propylene-diene rubber (EPDM); thermosetting resins such as epoxy resin and phenol resin; polyethylene wax, paraffin Waxes such as wax; ethylene-vinyl acetate copolymer (EVA), polyethylene, polypropylene, polyvinyl chloride (PVC), acrylic resin, thermoplastic polyurethane, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene- Styrene copolymer (ABS resin), polystyrene (PS), polyamide resin (nylon 6, nylon 66, etc.), polycarbonate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyacetal (POM) Thermoplastic resins such as polyphenylene sulfide (PPS); ionomer resins such as ethylene ionomer, urethane ionomer, styrene ionomer, and fluorine ionomer; thermoplastic elastomers such as olefin elastomer and styrene elastomer; polylactic acid (PLA); Bioplastics such as cellulose acetate, PBS, PHA, starch resin; Sealing materials such as modified silicone, urethane, polysulfide, acrylic, silicone, polyisobutylene, butyl rubber; urethane, ethylene-vinyl acetate copolymer Physical, vinyl chloride and acrylic coating components; inorganic materials such as cement, mortar and cordierite.

The composition of the present invention can be prepared by mixing these base components with thermally expandable microspheres and / or hollow particles.
Examples of the use of the composition of the present invention include a molding composition, a coating composition, a clay composition, a fiber composition, an adhesive composition, and a powder composition.

The composition of the present invention is a compound having a melting point lower than the expansion start temperature of the thermally expandable microsphere and / or a thermoplastic resin (for example, polyethylene wax, paraffin wax, in particular, as a base component together with the thermally expandable microsphere. Waxes such as ethylene-vinyl acetate copolymer (EVA), polyethylene, polypropylene, polyvinyl chloride (PVC), acrylic resin, thermoplastic polyurethane, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene Thermoplastic resins such as copolymer (ABS resin), polystyrene (PS), polycarbonate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT); ethylene ionomer, urethane ionomer, styrene ionomer, fluorine Ionomer resins such as ionomer; may include olefinic elastomers, thermoplastic elastomers) such as styrene elastomer can be used as a master batch for a resin molded. In this case, this resin molding masterbatch composition is used for injection molding, extrusion molding, press molding, and the like, and is suitably used for introducing bubbles during resin molding. The resin used at the time of resin molding is not particularly limited as long as it is selected from the above base material components. For example, ethylene-vinyl acetate copolymer (EVA), polyethylene, polypropylene, polyvinyl chloride (PVC), acrylic resin , Thermoplastic polyurethane, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene (PS), polyamide resin (nylon 6, nylon 66, etc.), polycarbonate, polyethylene terephthalate ( PET), polybutylene terephthalate (PBT), ionomer resin, polyacetal (POM), polyphenylene sulfide (PPS), olefin elastomer, styrene elastomer, polylactic acid (PLA), cellulose acetate, PB , PHA, starch resins, natural rubber, butyl rubber, silicone rubber, ethylene - propylene - diene rubber (EPDM), etc., and, mixtures thereof, and the like. If necessary, known hindered phenol-based, sulfur-based, phosphorus-based antioxidants; hindered amine-based, triazole-based, benzophenone-based, benzoate-based, nickel-based, salicyl-based light stabilizers; Molecular weight regulators such as peroxides; organic and inorganic nucleating agents; neutralizing agents; antacids; antibacterial agents; fluorescent whitening agents; inorganics such as glass fibers, carbon fibers, silica fibers, and alumina fibers Fibrous material; wood powder; flame retardant; lubricant; colorant; carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, kaolin, talc, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, Inorganic fillers such as zinc oxide, alumina, calcium carbonate, barium carbonate; hydrolysis inhibitors; antistatic agents; ammonium carbonate, sodium bicarbonate, anhydrous sodium nitrate, etc. Inorganic chemical foaming agents; dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, benzenesulfonyl hydrazide, p, p′-oxybis (benzenesulfonylhydrazide), azodicarboxamide, etc. An organic chemical foaming agent; a foaming aid of a chemical foaming agent such as urea, organic acid, or metal salt; may contain reinforcing fibers such as glass fiber or carbon fiber.
When the heat-expandable microspheres of the present invention, azodicarboxamide, and metal salt-based foaming aids are used for resin molding, they are particularly suitable for applications where there is little discoloration and the final product requires whiteness.
The molded product of the present invention is obtained by molding this composition. Examples of the molded article of the present invention include molded articles such as molded articles and coating films. In the molded product of the present invention, various physical properties such as lightness, porosity, sound absorption, heat insulation, low thermal conductivity, low dielectric constant, design, impact absorption, and strength are improved.

Further, in the molded article of the present invention, discoloration due to heat treatment at high temperature is preferably suppressed, and the yellowing degree (ΔYI) of the molded article is preferably 30 or less, more preferably 25 or less, and even more preferably 20 Hereinafter, it is particularly preferably 15 or less, further preferably 10 or less, and most preferably 5 or less. The yellowing degree (ΔYI) of the molded product can be obtained by the method shown in the following examples, similarly to the yellowing degree of the thermally expandable microspheres.
A ceramic filter or the like can be obtained by further firing a molded product containing an inorganic substance as a base component.

Below, the Example of the thermally expansible microsphere of this invention is described concretely. The present invention is not limited to these examples. In the following Examples and Comparative Examples, “%” means “% by weight” unless otherwise specified.
With respect to the heat-expandable microspheres, hollow particles, compositions and molded products mentioned in the following examples and comparative examples, the physical properties were measured in the following manner, and the performance was further evaluated. Hereinafter, the heat-expandable microsphere may be referred to as “microsphere” for simplicity.

[Average particle size and particle size distribution]
A laser diffraction particle size distribution analyzer (HEROS & RODOS manufactured by SYMPATEC) was used. The dispersion pressure of the dry dispersion unit was 5.0 bar and the degree of vacuum was 5.0 mbar, measured by a dry measurement method, and the D50 value was taken as the average particle size.

[Water content of microspheres]
As a measuring apparatus, a Karl Fischer moisture meter (MKA-510N type, manufactured by Kyoto Electronics Industry Co., Ltd.) was used for measurement.

[Measurement of encapsulation rate of foaming agent enclosed in microspheres]
1.0 g of microspheres were placed in a stainless steel evaporation dish having a diameter of 80 mm and a depth of 15 mm, and the weight (W ₁ ) was measured. 30 ml of DMF was added and dispersed uniformly. After standing at room temperature for 24 hours, the weight (W ₂ ) after drying under reduced pressure at 130 ° C. for 2 hours was measured. The encapsulation rate (CR) of the foaming agent is calculated by the following formula.
CR (wt%) = (W ₁ −W ₂ ) (g) /1.0 (g) × 100− (water content) (wt%)
(In the formula, the moisture content is measured by the above method.)

[Measurement of the maximum expansion temperature of thermally expandable microspheres]
As a measuring device, DMA (DMA Q800 type, manufactured by TA instruments) was used. Prepare a sample by placing 0.5 mg of microspheres in an aluminum cup with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, and placing an aluminum lid with a diameter of 5.6 mm and a thickness of 0.1 mm on top of the microsphere layer. did. The sample height (H ₀ ) was measured with a force of 0.01 N applied to the sample from above with a pressurizer. A maximum expansion temperature (H) indicating the maximum sample height (H) in the vertical direction of the pressurizer is heated from 20 to 300 ° C at a heating rate of 10 ° C / min with a force of 0.01 N applied by the pressurizer. Tm) was measured. The maximum displacement (Hm) of the microsphere is calculated by the following equation.
Hm = H−H ₀

[The gelation rate of thermally expandable microspheres in DMF]
The thermally expandable microspheres were immersed in DMF for 72 hours, and the gelation rate in a DMF solvent was measured.
Specifically, 1.0 g of thermally expandable microspheres was added to a screw tube having a capacity of 100 cc, and the weight (W1) of the screw tubes and thermally expandable microspheres was weighed. The solution was filled with 30 ml of DMF and allowed to stand for 72 hours. After 72 hours, centrifugation was carried out at 2000 rpm for 2 minutes to separate the solvent and thermally expandable microspheres. After removing the solvent in the supernatant, drying in a vacuum isothermal phase, weighing the weight (W2) of the screw tube and the thermally expandable microspheres after removing all the solvent, and determining the dry weight of the gel (W = W1-W2) The gelation rate was calculated from the following formula.
Gelation rate = (Dry weight of gel (W) / Weight of polymer contained in 1 g of sample) × 100

[Measurement of loose bulk density]
A stainless steel cup with an inner diameter of 50 mm and an internal volume (V) of 100 cc was prepared, and its weight (Wb) was measured. Thermally expandable microspheres passed through a JIS 24-mesh sieve are uniformly added from above (23 cm) to the inside of the stainless steel cup, supplied to the upper edge of the stainless steel cup, and the thermally expandable microspheres are rubbed on the upper surface of the stainless steel cup. After cutting, the weight (Wa) of the stainless steel cup containing the thermally expandable microspheres was measured. The loose bulk density (ρa) was calculated from the following formula.
ρa = (Wa−Wb) / V

[Measurement of compacted bulk density]
The solid bulk density (ρb) is determined by the above loose bulk density measurement procedure, further supplying the thermally expandable microspheres from the top of the stainless cup filled with the thermally expandable microspheres, and tapping the thermally expandable microspheres. Refers to the bulk density when the is closely packed. Here, tapping means that a stainless cup filled with thermally expandable microspheres is repeatedly dropped from a certain height (tap height) onto the equipment floor (tapping table) to give a light impact to the bottom of the stainless cup. This refers to the operation of closely packing the thermally expandable microspheres into a stainless steel cup.
Actually, after measuring the loose bulk density, a cylinder having the same diameter as the stainless cup (no bottom caps at both ends of the cylinder) was attached to the top of the stainless cup filled with the thermally expandable microspheres. Then, thermally expandable microspheres were added from the upper end of the cylinder until it overflowed. Thereafter, tapping with a tap height of 1.8 cm was performed 180 times. After completion of tapping, the cylinder was removed, and the thermally expandable microspheres were scraped on the upper surface of the stainless cup, and the weight (Wc) of the stainless cup containing the thermally expandable microspheres was measured. The firm bulk density (ρb) was calculated from the following formula.
ρb = (Wc−Wb) / V
The loose bulk density and the hard bulk density were measured using a multi tester (MT-10001K) manufactured by Seishin Enterprise Co., Ltd.

(Measurement of compressibility)
“Compression degree” is a value indicating the degree of bulk reduction due to tapping, and the compression degree was calculated from the following equation.
Compressibility (%) = 100 × (ρb−ρa) / ρb

(Measurement of yellowing degree)
The yellowing degree (ΔYI) of the measurement sample is the yellowness (YI) after heating the measurement sample at 180 ° C. for 10 minutes using the color difference meter CR-400 manufactured by Konica Minolta, and the yellowness of the standard sample. It is a value indicating the degree of yellowing when compared with (YI0), and the yellowness and yellowing were calculated by the following equations. The standard sample was a white sample piece for calibration attached to the color difference meter CR-400.
Yellowness (YI) = 100 (1.2985X-1.1335Z) / Y
X, Y, Z: Tristimulus values in the XYZ color system when the standard illuminant D65 is used Yellowness (ΔYI) = YI−YI0

[Calculation of expansion ratio of molded product]
The density (D1) of the molded product obtained using the thermoplastic elastomer composition by the immersion method using the precision hydrometer AX200 (manufactured by Shimadzu Corporation) and the density (D2) of the thermoplastic elastomer composition before molding ) Were measured respectively. The expansion ratio was calculated from D1 and D2 by the following equation.
Expansion ratio (times) = D2 / D1

[True specific gravity of hollow particles with fine particles]
The true specific gravity of the fine particle-attached hollow particles (hereinafter simply referred to as hollow particles) was measured by an immersion method (Archimedes method) using hexane in an atmosphere at an ambient temperature of 25 ° C. and a relative humidity of 50%.
Specifically, the volumetric flask with a capacity of 100 cc was emptied and dried, and the weight of the volumetric flask (WB1) was weighed. After accurately filling the weighed measuring flask with hexane to the meniscus, the weight (WB2) of the measuring flask filled with 100 cc of hexane was weighed.

Further, the volumetric flask with a capacity of 100 cc was emptied and dried, and the weight of the volumetric flask (WS1) was weighed. The weighed volumetric flask was filled with about 50 cc of hollow particles, and the weight of the volumetric flask (WS2) was weighed. Then, the weight (WS3) after accurately filling the meniscus with hexane so that bubbles do not enter the volumetric flask filled with the hollow particles was weighed. Then, the obtained WB1, WB2, WS1, WS2 and WS3 were introduced into the following equation, and the true specific gravity (d) of the hollow particles was calculated.
d = [(WS2-WS1) × (WB2-WB1) / 100] / [(WB2-WB1)-(WS3-WS2)]

[Example 1; Production of thermally expandable microspheres]
465 g of ion-exchanged water, 116 g of sodium chloride, 40 g of colloidal silica that is 20% by weight of silica active ingredient, 2 g of polyvinylpyrrolidone and 4 g of an aqueous solution of ethylenediaminetetraacetic acid and 4Na that is 5% of active ingredient, aluminum chloride that is 5% of active ingredient After adding 2 g of an aqueous solution, the pH of the resulting mixture was adjusted to 2.8 to 3.2 to prepare an aqueous dispersion medium.
Separately, 40 g of acrylonitrile, 100 g of methyl methacrylate, 30 g of acrylic acid, 30 g of methacrylic acid, 0.6 g of trimethylolpropane trimethacrylate, 30 g of isopentane, 30 g of isooctane, and 8 g of di-2-ethylhexyl peroxydicarbonate are mixed. To prepare an oily mixture.

The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was then dispersed for 2 minutes at a rotational speed of 10,000 RPM using a homomixer to prepare an aqueous suspension. This aqueous suspension was transferred to a pressurized reactor having a capacity of 1.5 liters, purged with nitrogen, brought to an initial reaction pressure of 0.4 MPa, and polymerized at a reaction temperature of 55 ° C. for 15 hours while stirring at 150 rpm. The obtained polymerization product was filtered and dried to obtain thermally expandable microspheres A. Then, the maximum expansion temperature, gelation rate, loose bulk density, hard bulk density, compressibility, and yellowing degree were evaluated and are shown in Table 1.
The thermally expandable microsphere A was photographed with a scanning electron microscope (VE-8800 manufactured by Keyence Corporation, acceleration voltage 20 kV, magnification 30 times). When the shape of the thermally expandable microsphere was observed using the obtained electron micrograph, it was almost spherical, and no concave microsphere was observed.

[Examples 2 to 13 and Comparative Examples 1 to 4; Production of thermally expandable microspheres]
In Examples 2 to 13 and Comparative Examples 1 and 2, various components constituting the oily mixture used in Example 1 and the amounts thereof, and the polymerization temperature were changed in the same manner as shown in Tables 1 and 2. Polymerized. In Examples 2 to 13 and Comparative Examples 1 and 2, thermally expandable microspheres B to E, J to Q, and thermally expandable microspheres FG were obtained, respectively. Next, the maximum expansion temperature, gelation rate, loose bulk density, hard bulk density, compressibility, and yellowing degree were evaluated and are shown in Tables 1 and 2.
In Comparative Examples 3 and 4 as well, various components constituting the oily mixture used in Example 1 and the amounts thereof, and the polymerization temperature were similarly changed to those shown in Table 1 to produce thermally expandable microspheres. Tried.
However, in Comparative Example 3, no thermally expandable microspheres were obtained, and the oily mixture solidified. In Comparative Example 4, microspheres I were obtained, but did not exhibit expansibility.

Similarly to the thermally expandable microsphere A, the thermally expandable microspheres B to E, J to Q, and the thermally expandable microspheres F to G and I were photographed with a scanning electron microscope. Using VE-8800 (manufactured by Keyence Co., Ltd.), an electron micrograph was obtained under the conditions of an acceleration voltage of 20 kV and a magnification of 30 times. When the shape of the heat-expandable microsphere was observed using the obtained electron micrograph, all of the heat-expandable microspheres B to E and J to Q were almost spherical, and the recessed microsphere was observed. There wasn't. On the other hand, in all of the thermally expandable microspheres F to G and I, about 5% of the total microspheres were almost spherical, but the remaining microspheres were concave.
[Manufacture of master batch]
A masterbatch containing the thermally expandable microspheres obtained above was also prepared. 200 g of thermally expandable microspheres D obtained in Example 4 and 200 g of ethylene-vinyl acetate copolymer (melting point 61 ° C.) as a resin were melted at 75 ° C. using a pressure kneader having a mixing capacity of 0.5 L. Mixed. Here, workability was good when mixed with resin. Thereafter, the obtained mixture was pelletized into a size of 3 mm in diameter and 3 mm in length to prepare a master batch D (MB-D) containing 50% by weight of thermally expandable microspheres D.
For the thermally expandable microspheres A to C, E and J to Q obtained in Examples 1 to 3 and 5 to 13, master batches A to C, E and J to Q were prepared in the same manner as the master batch D. did. Again, workability was good when mixed with resin. Further, for the thermally expandable microspheres F and G obtained in Comparative Examples 1 and 2, master batches F and G were produced in the same manner as the master batch D.

[Manufacture of molded products]
94 parts by weight of low density polyethylene (Dow Chemical Japan Co., Ltd., DNDV-0405R, melting point 108 ° C., density 0.914) and 6 parts by weight of the master batch D (MB-D) obtained above were uniformly To prepare a low density polyethylene composition.
Subsequently, the low-density polyethylene composition is subjected to an 85t injection molding machine (manufactured by Nippon Steel Works, model: J85AD, with a shut-off nozzle: the expansion of thermally expandable microspheres in the cylinder is suppressed to stabilize the weight) The foamed molded product D was obtained by performing injection molding at a molding temperature of 170 ° C. The expansion ratio of the obtained molded product was 2.3 times. Moreover, when the yellowing degree ((DELTA) YI) of the obtained molded object D was measured, it was -1.
Low density polyethylene compositions were prepared using master batches A to C, E and J to Q in the same manner as master batch D. Next, moldings A to C, E, and J to Q were obtained in the same manner as the molding D, and the degree of yellowing (ΔYI) was measured and shown in Tables 1 and 2.

[Production of fine particle-attached hollow particles]
25 L of thermally expandable microspheres A obtained in Example 1 and 75 g of heavy calcium carbonate (manufactured by Asahi Minesue, MC-120) were mixed, and 2 L of Separa heated in advance to 90-110 ° C. with a mantle heater. Added to the bull flask. Next, the mixture was stirred at a speed of 600 rpm using a stirring blade of polytetrafluoroethylene (length: 150 mm) so that the true specific gravity became (0.12 ± 0.03) g / cc in about 5 minutes. The heating temperature was set to prepare fine particle-attached hollow particles A. When the true specific gravity was measured, it was 0.09 g / cc. Further, the yellowing degree (ΔYI) of the obtained fine particle-attached hollow particles A was measured and found to be 18.
For the heat-expandable microspheres B to G and J to Q obtained in Examples 2 to 13 and Comparative Examples 1 to 2, the fine particle-attached hollow particles B to G and J to Q are the same as the fine particle-attached hollow particles A. Was made.

The heat-expandable microspheres of Examples 1 to 13 are almost spherical, have excellent expandability, and have good workability when mixed with resin. Further, the yellowing degree (ΔYI) of the thermally expandable microspheres was small, the gelation rate was low, and the degree of compression was also small.
On the other hand, in Comparative Example 1, there were many nitrile monomers, and many concave microspheres were confirmed by observation with an electron microscope. Further, the degree of yellowing (ΔYI) of the thermally expandable microspheres was large, the gelation rate was high, and the degree of compression was also large.
In Comparative Example 2, since the blowing agent did not contain hydrocarbons having 8 or more carbon atoms, the same results as in Comparative Example 1 were obtained. In particular, the reason why dents were generated in the thermally expandable microspheres is considered to be due to the high vapor pressure of isobutane used as a foaming agent during the polymerization.

In Tables 1 and 2, the monomer component, initiator and cross-linking agent are indicated by the following abbreviations. The values in parentheses indicate the glass transition temperature of the homopolymer.
AN: Acrylonitrile (125 ° C)
MAN: Methacrylonitrile (120 ° C)
EMA: ethyl methacrylate (65 ° C.)
MMA: Methyl methacrylate (105 ° C)
AA: Acrylic acid (106 ° C)
MAA: Methacrylic acid (228 ° C)
MAAm: methacrylamide (165 ° C.)
PMI: N-phenylmaleimide (100 ° C. or higher)
TMP: trimethylolpropane trimethacrylate EDMA: ethylene glycol dimethacrylate 4EG-A: PEG400 # diacrylate OPP: di-2-ethylhexyl peroxydicarbonate AIBN: azobisisobutyronitrile

  The thermally expandable microspheres of the present invention can be used, for example, as a weight-reducing material such as putty, paint, ink, sealing material, mortar, paper clay, pottery, etc. It can be used for the production of a molded article having excellent sound insulation properties, heat insulation properties, heat insulation properties, sound absorption properties and the like by performing extrusion molding, press molding or the like.

11 Outer shell made of thermoplastic resin 12 Foaming agent 1 Hollow particle (fine particle-attached hollow particle)
2 Outer shell 3 Hollow part 4 Fine particles (adsorbed state)
5 Fine particles (indented, fixed state)

Claims (12)

A thermally expandable microsphere composed of an outer shell made of a thermoplastic resin and a foaming agent encapsulated therein and vaporized by heating;
The thermoplastic resin essentially comprises a methacrylic acid ester monomer and a carboxyl group-containing monomer, and the nitrile monomer has a total amount of 100 weights of the methacrylic acid ester monomer and the carboxyl group-containing monomer. Obtained by polymerizing 0 to 30 parts by weight of a polymerizable component,
The weight ratio of the methacrylic acid ester monomer is 40 to 85% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer,
The blowing agent is essentially a hydrocarbon having 8 or more carbon atoms,
Thermally expandable microspheres.   The thermally expandable microsphere according to claim 1, wherein the degree of compression is less than 25%.   The thermally expandable microsphere according to claim 1 or 2, wherein the gelation rate after being immersed in DMF for 72 hours is 90% or less. The thermally expandable microsphere according to any one of claims 1 to 3 , wherein the maximum expansion temperature is 100 ° C or higher. The thermally expandable microsphere according to any one of claims 1 to 4 , wherein a yellowing degree ΔYI when heated at 180 ° C for 10 minutes is 30 or less. A step of dispersing an oily mixture containing a polymerizable component, a foaming agent, and a polymerization initiator in an aqueous dispersion medium, and polymerizing the polymerizable component;
The polymerizable component essentially comprises a methacrylic acid ester monomer and a carboxyl group-containing monomer, and the nitrile monomer has a total amount of 100 weights of the methacrylic acid ester monomer and the carboxyl group-containing monomer. A polymerizable component that is 0 to 30 parts by weight with respect to parts,
The weight ratio of the methacrylic acid ester monomer is 40 to 85% by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer,
The blowing agent is essentially a hydrocarbon having 8 or more carbon atoms,
A method for producing thermally expandable microspheres. The thermally expandable microsphere according to claim 6 , wherein the polymerization initiator is 0.9 to 10 parts by weight based on 100 parts by weight of the total amount of the methacrylic acid ester monomer and the carboxyl group-containing monomer. Manufacturing method. In the polymerizable component, the crosslinking agent is 0 to 0.4 parts by weight with respect to 100 parts by weight of the total amount of the methacrylic acid ester monomer, the carboxyl group-containing monomer, and the nitrile monomer. Item 8. A method for producing a thermally expandable microsphere according to Item 6 or 7 . Inflating the heat-expandable microspheres according to any one of claims 1 to 5 is obtained by the hollow particles. A composition comprising the thermally expandable microspheres according to any one of claims 1 to 5 and at least one granular material selected from the hollow particles according to claim 9 , and a base material component. A molded article obtained by molding the composition according to claim 10 . The molded product according to claim 11 , wherein the yellowing degree ΔYI is 30 or less.

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